And a digital image with a text file accompanying it describing the image format is similarly resilient. Heck, you could provide text describing the format within the image file.
Also, I'll note that the comment I responded to specifically claimed that positive images last forever.
The problem isn't that it's digital. The problem is where do you store it? Hardrives, CDs, floppy disks? All of that stuff has a very limited lifetime, after which it simply stops working. And even if it continues to work, what are your chances of being able to buy a CD reader in five to ten years?
The big difference between analog and digital is that with analog, you can simply stuff it in a box and it will stay there. With digital, you have to take the time every now and then to make sure that you don't lose that stuff. And do you really think that you (or someone else, when you are gone) will be doing that properly? I mean, you will most likely have forgotten why that stuff was even "important" in a few years.
There's so much great stuff our generation is going to lose, simply because we'll forget to migrate our backups.
Also, I'll note that the comment I responded to specifically claimed that positive images last forever.